Method of manufacturing blockinglayer cells of the selenium type



April 4, 1950y J J A .VN AM 2,502,540

ST METHOD OF MANU TURING BLOCKI LAYER CELLS 0F THE SELENIUM TYPE Filed Sept. 21, 1945 fuwrnawbih wae.

l l l l I 0.6 ad a .is Z hwg/TOR l. 2 JOHAN/v5.5 maus ,Ax/inw Pww uwAMJrfL Patented Apr. 4, 1950 UNITED- vs'm'riss METHOD F MANUFACTURING BLOCKING-v. LAYER CELLS 0FV THE SELENIUM TYPE Johannes Jacobus Asnerns'V iloosv van v f Eindhoven, Netherlands, assigner to Hartford` National Bank & Trust Co., Hartford, .,COnn.,

as trustee Application september ai, 1945', sei-m1 No. 617.911

1n the Nemmeno, February 22, V194..

Section l, Public Law 690,-August 8,1946

` Patent expires February 22, 1963 s claims. (01,.'115-4366) This invention relates to a method ot manufacturing blocking-layer cells of the selenium type, particularly measuring rectiilers, in which a carrier plate has mounted on it a semi-conductive and a good conducting electrode. The semi-conductive electrode may be made for example of selenium, the good conducting one oi gold. The two electrodes are .generally assumed to be separated by a blocking layer. It has been suggested before to mount a lacquer nm upon such a cell after the good conducting electrode is placed inposition, inter alia in order to protect this electrode from the action of the` metal by means of which the current supply conductor was secured to the counter electrode as shown in my copending United States application, Ser. No. 617,578, now lPatent No. 2,446,254, issued August 3, 1948.

When ascertaining the relation existing with rectiiiers between the current transmitted in a forward direction and the voltage supplied, it is found that this current is comparatively lower at low voltages than at a higher voltage. When rectifying low voltages in general, this property is detrimental but particularly in the case of measuring rectiners a higher forward current is frequently endeavoured to be obtained even if small voltages are supplied. The scale division of the measuring instrument is thus given a more linear character.

'trode being placed in position and the cell is subjected to a heating up to a temperature ranging between 120 and 200 C. a considerable improvement of the properties of the cell in the` above-mentioned sense is obtained. Obviously,

'use should be made of a lacquer which is secure against the heating applied.

It is quite known per se and even the standard practice to immerse a rectiiier in an anti-corrosive lacquer after the good conducting electrode is placed in position. In addition, after lacquering these rectiers will generally be subjected to heating either deliberately in order to dry the lacquer or involuntarily while the rectiiier is in use. This heating will, however, be limited to the usual maximum operating temperature which lies at about 65 C. Such a temperature and even a higher temperature of, say, 80 C. is not liable to bring about the eilect achieved by the invention.

In a preferred embodiment of the invention heating is carried out at 170 C. for half an hour. Neither the temperature nor thev duration of the treatmentare, however, critical.

In order thatv the invention may be clearly understood and readily carried into effect it will now be describedY more fullyY with reference to the accompanying drawing in which: y

Fig. 1 is a `curve illustrating the voltage-current relationships in two cells, one of which is provided with 'a baked lacquer coating.

Fig. 2 is a curve illustratingv on a logarithmic scale the voltage-current relationship in two cells, in the region of low voltages, oneof the cells being provided with a bakedrlacquer coating, and

Fig. 3 illustrates one embodiment of a blocking layer cell which has been provided` with la lacquer coating which has been baked in airv at an elevatedv temperature.

Referring more particularly to Fig.- 3 of the drawing, a blocking layer cell constructed in accordance with the invention` is illustrated. A carrier plate I0 of galvanized aluminum is coated with a film of carbon which for the sake of clarity in the drawing is not shown. A layer oi' selenium II is applied to the carrier plate by casting after which the selenium is converted into the semi-conducting modification by a heat treatment in a heated press. .A blocking layer is then formed on the selenium layer which is extremely thin and is not illustrated in the drawing. Around gold electrode I2 having a diameter preferably between 1 and 3 mms. is applied to the selenium layer II by atomization of the gold after which the electrode assembly is sprayed with a solution of polystyrene. The polystyrene coating is baked in air at a temperature up to about for `half an hour forming a solid coating of'polystyrene I3 around the electrode assembly. The supply conductor I5 is secured to a metallic contact Il whichV has been applied to the. polystyrene layer I3 for making electrical contact to the gold electrode I2. For the sake of convenience, the layer of polystyrene has been greatly exaggerated, and it will be clearly understood that in the actual construction of the cell the thickness of the polystyrene lm is exceedingly thin.

The results are illustrated in the characteristic curves.

VIn the right-hand half of Fig. .l is plotted the forward current relatively to the voltage applied. The curve A relates to the properties of a cell which has not been subjected to heating, the curve B relates to a cell made by the method of the invention. The return current is plotted in the left-hand half of Fig. 1, the scale being,

3 however, diilerent from that ln the richt-hand half. It is clearly shown in this figure that the forward current increased, whereas the return current decreased.

In order better to bring out the dlil'erences in the region near the voltagesA of about 0.2 volt. Fig. 2 shows again the right-hand half of Fig. l, the currents being now plottedv on a logarithmic scale. It is obvious how the initial values are much higher with the curve B than with the curve A. It is this region which matters particularly with measuring rectiiiers.

What I claim is:

1. The method of manufacturing a blocking layer cell comprising the steps of forming a semiconductive electrode on a base, forming a blocking layer on said semi-conductive electrode, torming a conductive electrode on said blocking layer,

applying a coating of lacquer to the electrode assembly, and baking the lacquer at a temperature between about 100 and 200 C. until the lacquer has dried.

2. The method of manufacturing a blocking layer cell comprising the steps of forming a layer of selenium on a base, converting the selenium to a semi-conductive modification thereof, forming a blocking layer on said selenium layer, forming a conductive electrode on said blocking layer, applying a coating of polystyrene to the electrode assembly, and baking the polystyrene in air at a temperature of between approximately 100 to 200 C. until the polystyrene has dried.

3. The method of manufacturing a blocking layer cell comprising the steps of, forming a layer of selenium on a base, converting the selenium to a semi-conductive modication thereof, forming a blocking layer on said selenium layer. form- 4 ing a conductive electrode on ma blocking layer, applying a coating of polystyrene to the electrode assembly, and baking the polystyrene coating in air at a temperature of approximately 170 C. for approximately one half hour.

4. A blocking layer cell comprising a carrier plate. a semi-conductive electrode on said carrier plate, a blocking layer on said semi-conductive electrode, a conductive electrode on said blocking layer, and a coating of baked lacquer covering the electrode assembly.

5. A blocking layer cell comprising a carrier plate. a layer of selenium on said carrier plate, a blocking layer on said selenium layer, a conductive electrode of smaller cross-section than said selenium layer on said blocking layer, and a coating of baked polystyrene covering the electrode assembly.

JOHANNES JACOBUS ASUERUS PLOOS van AMSTEL.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,932,067 Duhme Oct. 24, 1933 2,134,131 Kipphan Oct. 25, 1938 2,182,377 Giuanella Dec. 5, 1939 2,345,122 Herrmann Mar. 28, 1944 2,419,602 Skinker et 8.1 Apr. 29, 1947 OTHER REFERENCES Transactions of the Electrochemical Society for 1945, pages 275-287. 

1. THE METHOD OF MANUFACTURING A BLOCKING LAYER CELL COMPRISING THE STEPS OF FORMING A SEMICONDUCTIVE ELECTRODE ON A BASE, FORMING A BLOCKING LAYER ON SAID SEMI-CONDUCTIVE ELECTRODE, FORMING A CONDUCTIVE ELECTRODE ON SAID BLOCKING LAYER, APPLYING A COATING OF LACQUER TO THE ELECTRODE ASSEMBLY, AND BAKING THE LACQUER AT A TEMPERATURE BETWEEN ABOUT 100* AND 200*C. UNTIL THE LACQUER HAS DRIED. 